High resolution electron microscopic immunolabeling of recently cloned proteins now permits clear identification of sites mediating brain functions that are affected in neurological and neurophychiatric diseases. This unique capability, together with a greater demand for quantitative ultrastructural data, has produced an unprecedented need for the use of a modern transmission electron microscope (TEM) by the faculty within the Departments of Neurology and Neuroscience and Pharmacology at Weill Medical College of Cornell University (WMC-CU). Original studies from this group have provided fundamental information on the subcellular distribution of neurotransmitter transporters and receptors using primarily a 1973 model of a Philips 201 TEM, which has become obsolete and unable to cost-effectively meet the needs of the investigators. This proposal requests funds to purchase a new TEM (Tecnai 12 BioTwin) with a digital camera and capacity for on-line imaging and quantitative analysis. The availability of this technologically advanced system will assure the completion of major biomedical research projects that are funded from several different branches of the NIH. These funds cannot be obtained from the research grants of any one investigator, and are not available except through the NIH Shared Instrument Program. The funded projects of the six principal investigators (P.I.'s) who comprise the major users group in this proposal rely exclusively on a TEM for data analysis. These studies require the use of a TEM for quantitatively determining the normal subcellular distribution and drug- or lesion-induced changes in the targeting of opioid receptors and other functional proteins within the rat central nervous system (CNS). The projects of six other investigators who comprise the minor users group require more limited, but crucial, on-line TEM analysis of CNS antigens, particularly in genetic animal models of neurodegenerative diseases and drug addiction. Together, the results from these studies will have major implications for understanding the control of pain, autonomic functions, motivated behaviors, and memory in humans. To assure the successful long-term use of the new TEM system, the daily operation of the instrument will be managed by an internal advisory committee of all major users, and maintained by an experienced staff with the full support of the Medical College.